Changes in soil characteristics under different aged plantations of Corsican pine (pinus nigra) at Chopwell Woodland Park, Gateshead, UK

This study examines the pedogenic processes and temporal changes occurring in soils across six different aged plantations of Corsican pine (Pinus nigra), which were otherwise similar in their environmental characteristics, including geology, slope angle and aspect, altitude and land use history. A representative soil profile was sampled, on a horizon basis, and a further 10 topsoil samples were collected, on a grid basis, from each plantation. Properties determined in the laboratory included pH, organic carbon content, particle size distribution, exchangeable base content (Ca, Mg, K, Na), total free and organically-bound iron content, and lead and zinc concentrations. Morphological and chemical changes within the soil profiles were examined to shed light on the processes and pathways of soil formation, and one-way analysis of variance (ANOVA) was used to compare topsoil characteristics between the different plantations. Morphological and chemical changes within the soil profiles indicated that organic matter accumulation and mor humus formation, acidification, clay translocation (lessivage) and incipient podzolisation were the dominant pedogenic processes. There are very few systematic age-related changes in soil morphological or physical and chemical characteristics, possibly due to a combination of young stand ages, high topsoil variability, soil mixing due to drainage operations and silvicultural practices. There are, however, a number of statistically significant but non-systematic differences in soil properties between the different aged plantation blocks. Possible associations between these differences and age-related litter production and root growth, and silvicultural operations such as understory control, plantation thinning and selective harvesting are explored

Bacteroids in the Rhizobium-Legume Symbiosis Inhabit a Plant Internal Lytic Compartment: Implications for other Microbial Endosymbioses

All nitrogen-fixing bacteroids within legume root nodule cells are surrounded by a host-derived peribacteroid membrane. Components of this membrane are supplied directly by the ER and Golgi of the host cell. The peribacteroid space lies between the peribacteroid and bacteroid membranes and contains several activities typically found in vacuoles, namely; protease, acid trehalase, alpha-mannosidase isoenzyme II and protein protease inhibitor. Thus bacteroids inhabit an environment which fulfils the definition of a lysosome. Since the endosymbiotic organelles are morphologically different from the lytic compartment normally present in a root cortex cell (the central vacuole), it is proposed that they represent organ-specific modifications of lysosomes, analogous to the protein bodies of seeds. Perisymbiontic membranes are features common to all known plant endosymbioses (involving rhizobia, cyanobacteria, actinomycetes, vesicular-arbuscular mycorrhiza etc.) and the implications of this lead to the hypothesis that in all these cases the endosymbiont is compartmentalized within a specialized host lysosom

High-resolution 3D weld toe stress analysis and ACPD method for weld toe fatigue crack initiation

Weld toe fatigue crack initiation is highly dependent on the local weld toe stress-concentrating geometry including any inherent flaws. These flaws are responsible for premature fatigue crack initiation (FCI) and must be minimised to maximise the fatigue life of a welded joint. In this work, a data-rich methodology has been developed to capture the true weld toe geometry and resulting local weld toe stress-field and relate this to the FCI life of a steel arc-welded joint. To obtain FCI lives, interrupted fatigue test was performed on the welded joint monitored by a novel multi-probe array of alternating current potential drop (ACPD) probes across the weld toe. This setup enabled the FCI sites to be located and the FCI life to be determined and gave an indication of early fatigue crack propagation rates. To understand fully the local weld toe stress-field, high-resolution (5 mu m) 3D linear-elastic finite element (FE) models were generated from X-ray micro-computed tomography (mu-CT) of each weld toe after fatigue testing. From these models, approximately 202 stress concentration factors (SCFs) were computed for every 1 mm of weld toe. These two novel methodologies successfully link to provide an assessment of the weld quality and this is correlated with the fatigue performance

A simple model based on known plant defence reactions is sufficient to explain most aspects of nodulation

We present the following hypothesis; that lipo-oligochitin Nod-factors can act in an elicitor-like fashion inducing, amongst other effects, a plant chitolytic enzyme, capable of hydrolysing the oligochitin chain of the Nod-factor. Decorative groups on the oligochitin chain, e.g. sulphate, may confer partial resistance to hydrolysis upon particular Nod-factors. After entry into the plant, Nod-factor synthesis must be down-regulated in order to avoid further, unwanted, eli-citation and the consequent abortion of the symbiosis. The plant-derived compounds inhibiting the synthesis of bacterial Nod-factors are limiting in root tissue, leading to residual elicitation and the abortion of infection thread formation. Nod-gene anti-induction is, furthermore, inactivated by both light and nitrate, thus contributing to the inhibition of nodulation under these conditions. In nitrogen-fixing nodules, the bacteroids are exposed to both nod-gene inducing and repressing compounds. The slow accumulation of Nod-factors within the peribacteroid space eventually results in the elicitation of phytoalexin synthesis and nodule senescenc

Cauchy horizon singularity without mass inflation

A perturbed Reissner-Nordstr\"om-de Sitter solution is used to emphasize the nature of the singularity along the Cauchy horizon of a charged spherically symmetric black hole. For these solutions, conditions may prevail under which the mass function is bounded and yet the curvature scalar $R_{\alpha\beta\gamma\delta} R^{\alpha\beta\gamma\delta}$ diverges.Comment: typeset in RevTex, 13 page

Reducing Broiler Bruising on the Farm.

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